Single cell protein

I don't know anything about yeast, but a number of filamentous fungi
have modified to overexpress proteins of various sorts, including for human
food. Some of this is reviewed in Trinci, A.P.J. 1995. Pure and Applied
Mycology. Canadian J. Bot. 73 (Supplement 1): S1-S14.
Good Luck!
todell at u.washington.edu
Mycology is better than Urology!